Method of treating fluorine compound and treated substance

ABSTRACT

Divalent and trivalent metal salts are added to the solution containing the fluorine compound to precipitate the layered double hydroxide containing the fluorine compound between layers. By these processes, the fluorine compound can be fixed with high rate. Moreover, if necessary, the precipitated layered double hydroxide can be recovered to separate the fluorine compound or its salt between layers. Therefore, the burden to environment or the ecosystem by the fluorine compound can be reduced.

FIELD OF THE INVENTION

[0001] Present invention relates to a treatment process reducing aburden to environment and ecosystem about a solution containing amolecular anion having a per-fluorocarbon chain as a main component. Inaddition, it is preferable that said treatment process recovers theabove-mentioned anion to use effectively. Specifically, the presentinvention relates to a technology, which forms a layered doublehydroxide to fix the molecular anion having the per-fluorocarbon chainas a main component in the solution, and recovers to reproduce theseanions preferably.

BACKGROUND OF THE INVENTION

[0002] The anion surface-active agent having the per-fluorocarbon chainas a main component is used as an indispensable material of a productionprocess in many fields, such as an emulsion polymerization process ofPTFE (poly-tetra-fluoro-ethylene), and a production process of anelectronic parts industry. Moreover, said anion surface-active agent isalso widely used as a material, which are various paints, a coatingagent, and a fire-extinguishing agent, etc. However, in these productionprocesses, the above-mentioned anion surface-active agent has been usedas a dilute solution, such as several % to 0.01% by weight, so that theefficient fixing and recovering said anion on an industrial scale hasbeen difficult. Moreover, the problem of this fixing and recovering hasnot been considered in general because this solution is dilute.Furthermore, the fluorine compound, such as said anion surface-activeagent, is a hard material to be processed by the activated sludgeprocessing, which has been widely used as a wastewater processing.However, a harmony of chemical materials to environment or ecosystem isrequired strongly in recent years, and, also about this fluorinecompound, it is started that the necessity of the technology about theclosing system by fixing, recovering and reproducing is recognizedstrongly.

[0003] According to the fixing and recovering of this anionsurface-active agent, the technology using the layered double hydroxidehas been examined to be in practical use about a phosphate anion or anorganic anion, as a scavenger or a removal agent of anions. However,about molecular anion having the per-fluorocarbon chain as a maincomponent, such examinations have not been done previously. In addition,as a conventional technology, it is known that the process, in which anammonium salt of fluoroalkane acid is extracted to recover by using anorganic solvent, such as dichloro-methane or trichloro-methane, wasproposed (Japanese Patent Raid Open No. Shou 61-215346), but thisprocess uses an organic solvent containing chlorine, so that it is notenough for reducing the burden to environment.

[0004] In addition, the inventors have already reported the layereddouble hydroxide having anion between layers (Zn₂Al(OH)₆C₇F₁₅CO₂) forthe purpose of a material synthesis (the 76th spring annual meeting ofthe Chemical Society of Japan), about a high concentration aqueoussolution of per-fluoro-octanoic acid ammonium, i.e., about 8.6% byweight. However, this report was not for the purpose of fixing andrecovering of the anion like this invention, about the solution havingthe wide concentration range including the dilute solution of 0.1% byweight. Therefore, the process about fixing of such fluorine compoundhas not been reported yet.

DISCLOSURE OF THE INVENTION

[0005] Present invention provides the treatment process, in which anorganic fluorine compound having the per-fluorocarbon chain is fixedstably and easily, and its absorbing and fixing material. By thistreatment process and material, the burden to environment and ecosystemcan be reduced, and said fluorine compound can be used effectively asresources. Specifically, the present invention provides the treatmenttechnology fixing to recover efficiently the anion having theper-fluorocarbon chain as the main component, such as carboxylic acidion, sulfonic acid ion, etc., from the aqueous solution having the wideconcentration range including the dilute aqueous solution of 0.1% byweight.

[0006] That is, this invention provides the process comprising thefollowing constitution.

[0007] [1] A treatment process of a solution containing an organiccompound having a fluorocarbon chain (hereinafter said to as thefluorine compound), the process comprising,

[0008] adding divalent and trivalent metal salts to said solution,

[0009] forming a layered double hydroxide having the fluorine compoundbetween layers to absorb and fix the fluorine compound.

[0010] [2] A treatment process of a solution containing the fluorinecompound, the process comprising,

[0011] adding divalent and trivalent metal salts to said solution,

[0012] precipitating a layered double hydroxide having the fluorinecompound between layers,

[0013] separating a solid part by a solid-liquid separation,

[0014] dissolving said separated solid part in an acid, and

[0015] separating a fluorine compound or its salt.

[0016] [3] The treatment process of the solution containing the fluorinecompound according to above-mentioned process [1] or [2], the processfurther comprising,

[0017] adjusting pH of the solution to more than 4,

[0018] precipitating the layered double hydroxide having the fluorinecompound between layers.

[0019] [4] The treatment process of the solution containing the fluorinecompound according to above-mentioned process [1] or [2], the processfurther comprising,

[0020] adding an alkali to the solution to adjust pH from 4 to 12,

[0021] adding divalent and trivalent metal salts to said solution, and

[0022] precipitating the layered double hydroxide having the fluorinecompound between layers.

[0023] [5] The treatment process of the solution containing the fluorinecompound according to any one of above-mentioned processes [1] to [4],wherein the divalent metal salt is a salt of magnesium, calcium, zinc,nickel, copper, manganese (divalent), or cobalt (divalent), and thetrivalent metal salt is a salt of aluminum, iron, chromium, manganese(trivalent), cobalt (trivalent), potassium, lanthanum, or scandium.

[0024] [6] The treatment process of the solution containing the fluorinecompound according to any one of above-mentioned processes [1] to [5],wherein the divalent and the trivalent metal salts are chlorides.

[0025] [7] The treatment process of the solution containing the fluorinecompound according to any one of above-mentioned processes [1] to [6],wherein said fluorine compound is carboxylic acid or sulfonic acidhaving the fluorocarbon chain, in which the number of carbon is morethan 5.

[0026] [8] The treatment process of the solution containing the fluorinecompound according to any one of above-mentioned processes [1] to [7],wherein the layered double hydroxide having the fluorine compoundbetween layers is shown in the following formula [1].

M(II)_(1-X)M(III)_(X)(OH)₂Y_(X) /m.nH₂O  [1]

[0027] where Y is an anion having valence number m of the fluorinecompound having the fluorocarbon chain, M(II) is a divalent metal ion,M(III) is a trivalent metal ion, X is 0.1 to 0.5, and n is 0 or positiveinteger.

[0028] [9] A treatment process for recovering the fluorine compound andits salts, the process comprising,

[0029] precipitating the layered double hydroxide by the treatmentprocess according to any one of above-mentioned processes [1] to [7],

[0030] recovering the solid part by the solid-liquid separation,

[0031] dissolving said recovered solid part in a mineral acid to recoverthe

[0032] separated fluorine compound or its salts, or

[0033] heating said mineral acid dissolving the recovered solid part,

[0034] putting quietly to separate an oil layer, and

[0035] taking out the oil layer to recover the fluorine compound and itssalts.

[0036] [10] A treatment process for recovering a fluorine compound andits salts, the process comprising,

[0037] precipitating the layered double hydroxide by the treatmentprocess according to any one of above-mentioned processes [1] to [9],

[0038] recovering the solid part by the solid-liquid separation,

[0039] dispersing the recovered solid part to an organic solvent, and

[0040] filtering an insoluble part from said solvent.

[0041] According to the above-mentioned processes of the presentinvention, the fluorine compound can be fixed stably to form the layereddouble hydroxide having the fluorine compound between layers, by addingdivalent and trivalent metal salts to the solution containing thefluorine compound, such as the surface-active agent having theper-fluorocarbon chain. In addition, according to this treatmentprocess, even when the concentration of the anion aqueous solution ofthe surface-active agent having the per-fluorocarbon chain is less thanseveral % by weight, for example, very low concentration of about 0.01%by weight, this fluorine compound can be fixed with a very high rate ofmore than 90%. Moreover, as the adding metal salt, the safe salt toenvironment can be used, and the recovered layered double hydroxide is asolid, so that it can be processed advantageously in transportation orstorage by drying.

[0042] Hereafter, this invention is explained concretely.

[0043] (A) Formation of the Layered Double Hydroxide

[0044] Present invention is the treatment process, wherein the divalentand trivalent metal salts are added to the aqueous solution containingthe anion of the organic fluorine compound having the fluorocarbon chain(the fluorine compound), such as carboxylic acid ion or sulfonic acidion, etc., to form LDH containing said anion between the layers. By thisprocess, the above-mentioned anion is fixed between the layers of LDH toseparate this fluorine compound from the solution. Moreover, the presentinvention can be applied effectively to the solution containing thefluorine surface-active agent etc. as the fluorine compound having thefluorocarbon chain.

[0045] In the present invention, for example, the layered doublehydroxide having the fluorine compound between the layers is thecompound shown in the following formula [1]. In addition, it isavailable that this compound contains water or not.

M(II)_(1-X)M(III)_(X)(OH)₂Y_(X) /m.nH₂O  [1]

[0046] where, Y is the anion having the valence number m of the fluorinecompound having the fluorocarbon chain, M(II) is the divalent metal ion,M(III) is the trivalent metal ion, X is 0.1 to 0.4, and n is 0 orpositive integer.

[0047] The layered double hydroxide of above formula [1] having thefluorine compound between layers is, for example, the compound that theanion A is replaced by the fluorine compound Y having the fluorocarbonchain, in the compound of the following formula [2].

M(II)_(1-x)M(III)_(x)(OH)₂A_(x/m) .nH₂O  [2]

[0048] where, A is the anion having the valence number m, M(II), M(III),X, and n are the same as the formula [1].

[0049] The divalent metal ion is each ion of magnesium, calcium, zinc,nickel, copper, manganese (divalent), or cobalt (divalent). Moreover,the trivalent metal ion is each ion of aluminum, iron, chromium,manganese (trivalent), cobalt (trivalent), gallium, lanthanum, orscandium. In these compounds, since the chloride is easy to receive andits reaction effect is also good, it is preferable to be used. Moreover,it is also available that these metal salts are the mixed compoundshaving two or more kinds of ion respectively. As the anion having thevalence number m, carboxylic acid ion, sulfonic acid ion, chlorine ionand nitric acid ion etc. can be used.

[0050] The layered double hydroxide shown in the above-mentioned formula[1] can be formed by adjusting pH to more than 4, preferably 5 to 8, andadding the above-mentioned divalent and trivalent metal salts to theaqueous solution of the fluorine compound having the fluorocarbon chain.In addition, it is preferable that the addition of the metal salts isafter or the same time at the adjustment of pH. Specifically, forexample, the above-mentioned layered double hydroxide is precipitated bythe way that the aqueous solution mixed with the above-mentioneddivalent and trivalent metal salts is dropped gradually in the aqueoussolution of the fluorine compound having the fluorocarbon chain, untilthe mole ratio becomes to the formula [1], and simultaneously alkali isdropped gradually to adjust pH of the solution to more than 4,preferably 5 to 8. Moreover, as alkali, conventional sodium hydroxide,and potassium hydroxide etc. can be used. In addition, when the divalentmetal ion is calcium or magnesium, it is available that pH of theaqueous solution is in the range of 5 to 12. Regarding the addition ofthe divalent and trivalent metal salts, it is preferable that X value ofmole ratio is 0.1 to 0.5 in the above-mentioned formula [1]. Usually, ittakes about 3 hours for a natural precipitation of the separatedsubstance at room temperature. In addition, it is preferable that thesolution is stirred. The formed precipitate can be filtered to recover.

[0051] In the above-mentioned layered double hydroxide, the layereddouble hydroxide having the X value of about 0.33 in the formula [1], isnot only having the large amount of reception capacity (the absorptioncapacity), but also making the stable compound between the absorbedanion and itself. Therefore, said layered double hydroxide is the mostpreferable for fixing and recovering the absorbed anion. Moreover, bothof the divalent metal ion of zinc or magnesium and the trivalent metalion of aluminum or iron, which can form the layered double hydroxide,are safe and harmless to environment. In addition, chlorine ion and Naion used in the forming process of this layered double hydroxide arealso safe and harmless to environment. Furthermore, by controlling pH ofthe aqueous solution to near neutral, the influence to environment bythe wastewater can also be removed substantially.

[0052] In addition, as mentioned above, when the precipitate of thelayered double hydroxide having fluorine compound between layers isformed, before adjusting pH of the solution and adding the metal salts,it is preferable that the inert gas is bubbled beforehand in thesolution containing the fluorine compound and the polymer containingfluorine to drive out the carbonic acid contained in the solution. Ifthe carbonic acid is remained in the solution, the metal salts and thealkali will react with carbonic acid, so that it is not preferable.

[0053] According to the above-mentioned process for forming the layereddouble hydroxide, the objective anion of the fluorine compound havingthe fluorocarbon chain can be fixed with high efficiency of more than60%, preferably more than 90%. In addition, the formed precipitatecontaining the layered double hydroxide can be separated by theconventional method of the solid-liquid separation. As the concreteseparation equipment or method, for example, the filtering, adecantation, a centrifugation, a thickener, a filter press, a precoat,and a body field, etc. can be used. In addition, it is not limited tothese.

[0054] (B) Recovering the Fluorine Compound.

[0055] The process for separating the fluorine compound from therecovered layered double hydroxide shown with the formula [1] is thefollowings. The precipitate of this layered double hydroxide isdissolved in the mineral acid having pH of less than 1. At this time,since the fluorine compound is remained in the strong acid withoutdissolving, this remained fluorine compound is recovered by thesolid-liquid separation. On the other hand, when the liquid temperatureof this solution is more than the fusion temperature of the fluorinecompound or its salt, since this fluorine compound is liquefied, thefluorine compound or its salt can be recovered by putting quietly totake out the separated oil layer.

[0056] Specifically, for example, the precipitated layered doublehydroxide is recovered by the solid-liquid separation, and the recoveredsubstance is dissolved in sulfuric acid etc. having pH of less than 1.At this time, the divalent and trivalent metal components in the layereddouble hydroxide are dissolved. Moreover, when the liquid temperature ishigher than the fusion temperature of the fluorine compound or its salt,the fluorine compound or its salt is liquefied. Therefore, as puttingquietly this solution at more than the above-mentioned fusiontemperature, the water layer containing the divalent and trivalent metalions and the oil layer containing the fluorine compound or its salt canbe separated to take out this oil layer. The fluorine compound, such ascarboxylic acid, can be recovered with high purity and high yield byrefining this oil layer by distillation etc.

[0057] In addition, when the precipitated layered double hydroxide ismixed with sulfuric acid etc. having pH of less than 1, the temperatureof the solution is raised by heating of dilution. From this reason, whenthe liquid temperature becomes more than the fusion temperature of thefluorine compound or its salt, it is preferable that this solution isput quietly to keep this temperature. Moreover, when the liquidtemperature is low, it is preferable that said liquid is heated, so thatit may become more than the fusion temperature. According to suchseparation of liquid and liquid, the fluorine compound can be separatedmore advantageously than the solid-liquid separation.

[0058] As another process, it is also available that the fluorinecompound is separated as the solid part, by the solid-liquid separationof the solution, where the precipitate was dissolved in the strong acidat the liquid temperature of less than the above-mentioned fusiontemperature.

[0059] The recovery process using an ion exchange can be used other thanthe above-mentioned process, which dissolves the precipitate in thestrong acid. That is, the precipitate containing the layered doublehydroxide etc., which is separated by the solid-liquid separation, isdispersed in the aqueous solution of carbonate, such as sodiumcarbonate. At this time, the divalent and trivalent metal ions, whichhas been fixed in the layered double hydroxide, are ion-exchanged by thecarbonate ion, and to be eluted in the liquid. Then, the solid part isrecovered by the solid-liquid separation of said solution, and dissolvedin an alcohol. The insoluble part in the alcohol is filtered, so thatthe fluorine compound or its salt can be recovered.

[0060] (C) Application

[0061] According to the treatment process of the present invention,wherein the fluorine compound can be absorbed and fixed by forming thelayered double hydroxide having the fluorine compound between layers,the process can be developed into the various methods, such as the ionexchanging method, in which the fluorine compound is absorbed and fixedon the preformed layered double hydroxide having good ion exchangeability shown in the above-mentioned formula [2], and a re-hydratingmethod, in which the solid part formed by the above-mentioned absorbedand fixed process, i.e. the absorbing and fixing material, is baked toreproduce the absorption ability for reusing, etc.

[0062] As mentioned above, in the treatment process of the presentinvention, although the compound between LDH layers is formed as thefixing compound, in this structure, the positive charged metal hydroxidelayer and the anion layer compensating the positive charge, arelaminated between said metal hydroxide layers. The schematic structureof this layered double hydroxide is shown in FIG. 3. It has been knowngenerally that the characteristics of this structure have a function asthe ion exchange between anions and an anion scavenger. However, byusing this structure, the present invention provides the preferablestate for the solid layer formation by the self-coagulation-interaction(hydrophobic bond) of the per-fluorocarbon chain having a remarkablehydrophobic property, with a micro level. By providing the preferablestate, the present invention fixes the objective anion stably betweenlayers, by using the multiplication-effect between the self-coagulationinteraction of the per-fluorocarbon chain and the electrostaticinteraction between layers of the layered double hydroxide. Such ideasof the present invention have not been known conventionally.

BRIEF EXPLANATION OF THE FIGURES

[0063]FIG. 1 shows the IR spectrum ratio of the precipitate (a) atending time of dropping, and (b) after putting quietly for one whole dayand night, in Example 1.

[0064]FIG. 2 shows XRD patterns of the precipitate (a) at ending time ofdropping, and (b) after putting quietly for one whole day and night, inExample 1.

[0065]FIG. 3 is a schematic structure showing the layered doublehydroxide (recovered precipitate) of the present invention.

[0066] Hereinafter, the treatment process of the present invention isexplained concretely with the examples.

EXAMPLE 1

[0067] 1000 ml of the aqueous solution of per-fluoro-octanoic acidammonium (C₇F₁₅COONH₄) of 0.1% by weight, wherein the anion for thepurpose of absorption was 2.32 mmol, was put into the glass beaker, andthe mixed solution of zinc chloride and aluminum chloride, wherein Zn²⁺ion was 4.64 mmol and Al³⁺ ion was 2.32 mmol, was dropped gradually inthis solution. Simultaneously, 2 mol/l of the aqueous solution of sodiumhydroxide was also dropped to adjust pH to 7. This process was done for3 hours. Immediately after the dropping of the mixed aqueous solution,the aqueous solution became cloudy to form the white precipitate withprogress of time, and this liquid cloudiness was finished to completethe precipitate forming after 3 hours. The precipitate was filtered torecover, and dried at 70° C. until the constant weight to be 1.50 g.

[0068] 1 mg of this powder was taken, and the infrared absorptionspectrum was measured by the KBr tablet method. The result of thespectra is shown in FIG. 1. The spectra immediately after reaction isshown in FIG. 1(a), and the spectra after putting quietly one whole dayand night is shown in FIG. 1(b). In these spectra, the strong absorptionpeculiar to the per-fluorocarbon chain, and the absorption of a hydroxylgroup peculiar to LDH layer, were observed, so that it was confirmedthat these spectra were the layered double hydroxide(Zn₂Al(OH)₆C7F₁₅CO₂). By this chemical formula and weight, the amount ofanions in the solid layer was calculated to be 2.23 mmol, and thisamount was equivalent to 96.1% by weight of anions first dissolved inthe aqueous solution.

[0069] Moreover, the powder at the ending time of dropping was taken outto put on the glass plate to make a film for measuring by XRD. From theresult of XRD, the diffraction belonging to the basal plane space ofabout 3.0 nm was shown, and the high-dimension reflections belonging tothis diffraction were also shown. Considering the length of the absorbedanion, i.e. 1.25 nm, and the thickness of LDH, i.e. 0.48 nm, it wassupposed that the layered compound involving two molecules layer betweenlayers, was formed.

[0070] Moreover, the dried powder separated by putting quietly one wholeday and night after reaction, was measured by XRD. From the result ofXRD, the basal plane space was reduced to about 2.50 mm, and, at thepositions of 0.263 nm and 0.152, the reflections of (100) plane and(110) plane corresponding to hexagonal lattice in the LDH layer, wereobserved. These reflections indicated that the lattice constant [a] was0.304 nm, and the hydroxide layer, in which the ions of aluminum andzinc were mixed, was formed to grow up in this structure. Moreover, inthe sample (b), the basal plane space was reduced compared with theabove-mentioned sample (a), and the super lattice line corresponding tothe period of the twice length of the sample (a), was appeared. Fromthis result, it was supposed that the regulation of the anionarrangement between layers was advanced to transfer to the more closedstructure. In addition, when IR spectra of these both samples werecompared, there were no fundamental differences excepting that theabsorption band of the lattice vibration of the metal hydroxide layernear 430 cm⁻¹ was radicalized with improvement of the crystalregularity. Therefore, it was considered that this change was done bythe regulation of molecule arrangement in the structure, and theincorporation of the objective anion to the solid phase was finishedmostly at the time of the ending of dropping.

[0071] On the other hand, the solution after filtering the precipitate(the supernatant liquor), was measured by the calorimetric method usingmethylene blue. The calibration curve was made by following ways. Fivekinds of standard solution, in which 1 to 5 ppm by weight of ammoniumsalt of the above-mentioned negative ions was contained, were prepared,and 30 ml of said standard solution was taken respectively to theseparatory funnels to be added 10 ml of chloroform and 10 ml ofmethylene-blue solution. After shaking well, these solution were putquietly for 10 minutes and calibration curve was made by measuring theeach absorbance of these solutions using a visible/ultravioletspectrometer. The measuring wavelength was fixed at 635 nm. Theabsorbance value was in the range of 0 to 1 in this concentration range,and the calibration curve showed good linearity. The same process wasdone to the supernatant liquor. At this time, said supernatant liquorwas diluted to become in the range of 0 to 1 of the absorbance, ifnecessary. As a result, the concentration of the above-mentioned anionicsurface-active agent (per-fluoro-octanoic acid ammonium) was 10 ppm.This result means that 96% of the above-mentioned anions were fixed tothe initial concentration (0.1% by weight), and was corresponded withthe previous result by the solid weight. These results were shown inNo.1 of Table 1.

EXAMPLE 2

[0072] Regarding the aqueous solution, where the concentration wasdifferent from Example 1, the per-fluoro-octanoic acid ion was absorbedand fixed by the same process as Example 1. 100 ml of the aqueoussolution containing the objective anion ammonium salt of 1.0% by weight(the aqueous solution A), and 1.0 l of the aqueous solution containingsaid anion ammonium salt of 0.01% by weight (the aqueous solution B),were prepared respectively. In addition, 35 ml of the same mixedsolution of the zinc chloride and aluminum chloride as Example 1, wasdropped gradually in the aqueous solution A, and 3.5 ml of said mixedsolution was dropped gradually in the aqueous solution B. This processwas done for 3 hours. At this time, pH of the aqueous solutions of A andB were adjusted to 7 by using the sodium hydroxide of 2 mol/l. Thisdropping was done at room temperature, and the temperature was notcontrolled. After dropping, said aqueous solution was put quietlyovernight to filter the supernatant liquor, and the weight of the driedsolid part, the anion concentration, and the fixing ratio of anions,were measured like Example 1. These results were shown in No.2 of Table1.

EXAMPLE 3

[0073] The precipitate was formed like Example 1 excepting that themixed aqueous solution of zinc chloride and aluminum chloride was addedto the aqueous solution of per-fluoro-octanoic acid ammonium to adjustpH to 5. Then, 1.50 g of the precipitate was recovered by filtering anddrying. After forming the precipitate, the solution was put quietlyovernight to filter the supernatant liquor. Then, the weight of thesolid part after drying, the anion concentration, and the fixing ratioof anions, were measured like Example 1. These results were shown inNo.3 of Table 1.

EXAMPLE 4

[0074] The precipitate was formed like Example 1 excepting that about 35ml of the mixed aqueous solution of magnesium chloride and aluminumchloride, wherein Mg²⁺ ion was 4.64 mmol, and Al³⁺ ion was 2.32 mmol,was used as the mixed solution, and pH of the solution after droppingwas adjusted to 10. Then, 1.10 g of the precipitate was recovered byfiltering and drying. When the recovered precipitate was analyzed by XRDand the infrared absorption spectrum, it was confirmed that saidprecipitate was the layered double-hydroxide [Mg?Al(OH)₆C₇F₁₅CO₂]. Afterforming the precipitate, the solution was put quietly overnight tofilter the supernatant liquor. In addition, the weight of the solid partafter drying, the anion concentration, and the fixing ratio of anions,were measured like Example 1. These results were shown in No.4 of Table1.

EXAMPLE 5

[0075] The precipitate was formed like Example 1 excepting that about 35ml of the mixed aqueous solution of calcium chloride and aluminumchloride, wherein Ca²⁺ ion was 4.64 mmol, and Al³⁺ ion was 2.32 mmol,was used as the mixed solution, and pH of the solution after droppingwas adjusted to 10. Then, 0.85 g of the precipitate was recovered byfiltering and drying. When the recovered precipitate was analyzed byXRD, and the infrared absorption spectrum, it was confirmed that saidprecipitate was the layered double hydroxide [Ca₂Al(OH)₆C₇F₁₅CO₂]. Afterforming the precipitate, the solution was put quietly overnight tofilter the supernatant liquor. In addition, the weight of the solid partafter drying, the anion concentration, and the fixing ratio of anions,were measured like example 1. These results were shown in No.5 of Table1.

EXAMPLE 6

[0076] The precipitate was formed like Example 1 excepting that thesolution of per-fluoro-octyl sulfonic-acid ammonium (C₈F₁₇SO₃NH₄) of0.1% by weight, wherein the anion for the purpose of absorption was 2.32mmol, was used as the solution. Then, 1.70 g of the precipitate wasrecovered by filtering and drying. When the recovered precipitate wasanalyzed by XRD and the infrared absorption spectrum, it was confirmedthat said precipitate was the layered double hydroxide[Zn?Al(OH)₆C₈F₁₇SO₃]. After forming the precipitate, the solution wasput quietly overnight to filter the supernatant liquor. In addition, theweight of the solid part after drying, the anion concentration, and thefixing ratio of anions, were measured like Example 1. These results wereshown in No.6 of Table 1.

EXAMPLE 7

[0077] The precipitate was formed like Example 1 excepting that thesolution of per-fluoro-octyl sulfonic-acid lithium (C₈F₁₇SO₃Li) of 0.1%by weight, wherein the anion for the purpose of absorption was 2.32mmol, was used as the solution. Then, 1.45 g of the precipitate wasrecovered by filtering and drying. When the recovered precipitate wasanalyzed by XRD and the infrared absorption spectrum, it was confirmedthat said precipitate was the layered double hydroxide[Zn₂Al(OH)₆C₈F₁₇SO₃]. After forming the precipitate, the solution wasput quietly overnight to filter the supernatant liquor. In addition, theweight of the solid part after drying, the anion concentration, and thefixing ratio of anions, were measured like Example 1. These results wereshown in No.7 of Table 1.

EXAMPLE 8

[0078] 3 kg of dilute sulfuric acid having the concentration of 10 wt %,was put into the glass beaker, where the capacity was 3L, to add 300 gof the precipitate (the layered double hydroxide) recovered inExample 1. In addition, said solution was stirred to dissolve for 3hours at room temperature. After that, said dissolved solution was putquietly at 70° C., and the aqueous solution layer containing Zn ion andAl ion, and the oil layer comprising per-fluoro-octanoic acid, wereseparated. When this oil layer was taken out to distill, 172 g of themain fraction of per-fluoro-octanoic acid, wherein the temperature atthe top of the column was from 170 to 192° C., was recovered. The purityof this recovered substance was 99%, and the containing amount of Zn andAl was less than 1 ppm.

EXAMPLE 9

[0079] 400 g of the sodium carbonate aqueous solution having theconcentration of 10 wt %, was put into the glass beaker, where thecapacity was 500 ml, to add 20 g of the precipitate (the layered doublehydroxide) recovered in Example 1. In addition, said solution wasstirred to dissolve for 24 hours at room temperature. Then, 22.2 g ofcrystal was recovered by filtering and drying. This crystal was added to300 ml of methanol to be stirred for 1 hour at room temperature todisperse. The insoluble solid part was filtered to take out methanol bythe distillation from the filtrate. Then, 12.2 g of white crystal wasrecovered. When the insoluble solid part was analyzed by the IRspectrum, it was confirmed that the insoluble solid part comprised thesubstance that the anion parts of the layered double hydroxide werereplaced by the carbonate ions. Furthermore, it was also confirmed thatthe white crystal recovered by concentrating the filtrate has theper-fluoro-octanoic acid sodium as the main component.

EXAMPLE 10

[0080] The precipitate was formed like Example 1 excepting that theaqueous solution of per-fluoro-decanoic acid ammonium (C₉F₁₉COONH₄) of0.05% by weight, wherein the anion for the purpose of absorption was1.16 mmol, and the mixed aqueous solution of zinc chloride and aluminiumchloride, wherein Zn²⁺ ion was 2.32 mmol, and Al³⁺ ion was 1.16 mmol, inthe mixed solution, were used. Then, 0.84 g of precipitate was recoveredby filtering and drying. When this recovered precipitate was analyzed byXRD and the infrared absorption spectrum, it was confirmed that saidprecipitate was the compound containing per-fluoro-decanoic acidammonium (C₉F₁₉COONH₄). After forming the precipitate, the solution wasput quietly overnight to filter the supernatant liquor. The weight ofthe solid part after drying, the anion concentration, and the fixingratio of anions, were measured like Example 1. These results were shownin No.10 of Table 1.

INDUSTRIAL APPLICABILITY

[0081] According to the process of the present invention, it is possiblethat the fluorine compound, such as the surface-active agent having theper-fluorocarbon chain, can be absorbed and fixed stably between thelayers of the layered double hydroxide. The formation of the layereddouble hydroxide and the absorption of the fluorine compound areprogressed simultaneously in the solution, and this layered doublehydroxide is formed easily by adding the divalent and trivalent metalsalts, so that the above-mentioned fluorine compound can be absorbed andfixed easily. Moreover, in the suitable embodiment, when theconcentration of the anion aqueous solution of the surface-active agenthaving the per-fluorocarbon chain is less than several % by weight, forexample, very low concentration of about 0.01% by weight, this fluorinecompound can be fixed at a very high rate of more than 90%. In addition,as the adding metal salts, the safe ones to environment can be used.Moreover, since the layered double hydroxide can be recovered as asolid, it is advantageously in transportation or storage. Furthermore,according to the treatment process of the present invention, thefluorine compound fixed at the layered double hydroxide can be recoveredefficiently by the separation to be reused. Therefore, the burden toenvironment and ecosystem with the fluorine compound can be reduced, andthe fluorine compound can be reused as the resources. TABLE 1Precipitate Fluorine Compound Solution Anion Concentration, Amount ofAdditional Metal Salt Solution Anion Fixing No. Kinds Amount AnionDivalent Trivalent pH Amount Concentration Ratio 1 Per-fluoro-octanoicacid Aqueous solution of 2.32 mmol Zn Al 7 1.50 g 2.23 mmol 96.1%ammonium (C₇F₁₅COONH₄) 0.1%, 1000 ml 4.64 mmol 2.32 mmol 2Per-fluoro-octanoic acid Aqueous solution of 2.32 mmol Zn: Al: 7 1.50 g 2.3 mmol 99.1% ammonium (C₇F₁₅COONH₄) 0.1%, 100 ml 4.64 mmol 2.32 mmolAqueous solution of 0.232 mmol  Zn: Al: 0.15 g 0.21 mmol 91.0% 0.01%,1000 ml 0.464 mmol 0.232 mmol 3 Per-fluoro-octanoic acid Aqueoussolution of 2.32 mmol Zn Al 5 1.50 g 2.27 mmol   98% ammonium(C₇F₁₅COONH₄) 0.1%, 1000 ml 4.64 mmol 2.32 mmol 4 Per-fluoro-octanoicacid Aqueous solution of 2.32 mmol Mg Al 10 1.10 g  1.4 mmol   80%ammonium (C₇F₁₅COONH₄) 0.1%, 1000 mol 4.64 mmol 2.32 mmol 5Per-fluoro-octanoic acid Aqueous solution of 2.32 mmol Ca Al 10 0.85 g 2.3 mmol   60% ammonium (C₇F₁₅COONH₄) 0.1%, 1000 ml 4.64 mmol 2.32 mmol6 Per-fluoro-octyl-sulfonic acid Aqueous solution of 2.32 mmol Zn Al 71.70 g 2.23 mmol   99% ammonium (C₈F₁₇SO₃NH₄) 0.1%, 1200 ml 4.64 mmol2.32 mmol 7 Per-fluoro-octyl-sulfonic Aqueous solution of 2.32 mmol ZnAl 7 1.65 g 2.21 mmol   95% acid lithium (C₈F₁₇SO₃Li) 0.1%, 1174 ml 4.64mmol 2.32 mmol 10 Per-fluoro-decanoic acid Aqueous solution of 1.161mmol  Zn Al 7 0.84 g 1.09 mmol   94% ammonium (C₉F₁₉COONH₄) 0.005%, 1000ml 2.32 mmol 1.16 mmol

What is claimed is:
 1. A treatment process of a solution containing anorganic compound having a fluorocarbon chain (hereinafter said to as thefluorine compound), the process comprising, adding divalent andtrivalent metal salts to said solution, forming a layered doublehydroxide having the fluorine compound between layers to absorb and fixthe fluorine compound.
 2. A treatment process of a solution containingthe fluorine compound, the process comprising, adding divalent andtrivalent metal salts to said solution, precipitating a layered doublehydroxide having the fluorine compound between layers, separating asolid part by the solid-liquid separation, dissolving said separatedsolid part in an acid, and separating the fluorine compound or its salt.3. The treatment process of the solution containing the fluorinecompound according to claim [1] or [2], the process further comprising,adjusting pH of the solution to more than 4, precipitating the layereddouble hydroxide having the fluorine compound between layers.
 4. Thetreatment process of the solution containing the fluorine compoundaccording to claim [1] or [2], the process further comprising, adding analkali to the solution to adjust pH from 4 to 12, adding divalent andtrivalent metal salts to said solution precipitating the layered doublehydroxide having the fluorine compound between layers.
 5. The treatmentprocess of the solution containing the fluorine compound according toany one of claims [1] to [4], wherein the divalent metal salt is a saltof magnesium, calcium, zinc, nickel, copper, manganese (divalent), orcobalt (divalent), and the trivalent metal salt is a salt of aluminum,iron, chromium, manganese (trivalent), cobalt (trivalent), potassium,lanthanum, or scandium.
 6. The treatment process of the solutioncontaining the fluorine compound according to any one of claims [1] to[5], wherein the divalent and the trivalent metal salts are chlorides.7. The treatment process of the solution containing the fluorinecompound according to any one of claims [1] to [6], wherein the fluorinecompound is carboxylic acid or sulfonic acid having the fluorocarbonchain, in which the number of carbon is more than
 5. 8. The treatmentprocess of the solution containing the fluorine compound according toany one of claims [1] to [7], wherein the layered double hydroxidehaving the fluorine compound between layers is shown in the followingformula [1]. M(II)_(1-X)M(III)_(X)(OH)₂Y_(X/m) .nH₂O  [1] where, Y is ananion having valence number m of the fluorine compound having thefluorocarbon chain, M(II) is a divalent metal ion, M(III) is a trivalentmetal ion, X is 0.1 to 0.5, and n is 0 or positive integer.
 9. Atreatment process for recovering the fluorine compound and its salts,the process comprising, precipitating the layered double hydroxide bythe treatment process according to any one of claims [1] to [7],recovering the solid part by the solid-liquid separation, dissolvingsaid recovered solid part in a mineral acid to recover the separatedfluorine compound or its salts, or heating said mineral acid dissolvingthe recovered solid part, putting quietly to separate an oil layer, andtaking out the oil layer to recover the fluorine compound and its salts.10. A treatment process for recovering a fluorine compound and itssalts, the process comprising, precipitating the layered doublehydroxide by the treatment process according to any one of claims [1] to[7], recovering the solid part by the solid-liquid separation,dispersing the recovered solid part to an organic solvent, and filteringan insoluble part from said solvent.
 11. A layered double hydroxideshown by above-mentioned formula [1], which contains the fluorinecompound between layers and is formed by adding the divalent andtrivalent metal salts to the solution containing the fluorine compoundhaving the fluorocarbon chain.